On 23/11/20 11:01 am, Brecht Van Lommel wrote:
The solutions I'm suggesting are to either use a PointerProperty
(which will not become invalid), or store data on the object itself
rather than referencing the object.
Yes, these are perfect solutions in cases when they are sufficient. But
sometimes they cannot replace real unique identifier. I guess this is
why many end up just using object names since they are guaranteed to be
unique within single .blend file. And after putting a lot of effort to
write and optimize my own UID support I see why - it is just hard and
error prone to implement from scratch in an addon. It is also not
efficient, especially in large scenes, where looping through thousands
or tens of thousands of objects in Python is not fast at all (even if
the loop does not do much).
The question is if for example the Godot use case would be helped by
having it globally unique, so that e.g. renaming .blend files or
splitting .blend files into smaller ones also works.
I see. I guess this depends on the use case. I think the best solution
is to allow to reset UUID - then if somebody needs to make sure copies
of their objects are globally unique, they can do so by regenerating
their UUIDs. But if somebody wants them to stay stable, they do not need
to worry that renaming or copying .blend will break existing UUIDs.
Exporters usually export the evaluated objects rather than the
original ones, so it's an important case. One that at least would have
to be taken into account when someone contributes a patch for this.
We already have a mechanism for stable IDs for instances. I imagine
that can be combined with a stable UUID of the original datablock to
get a stable UUID for evaluated datablocks.
This sounds like a good idea. It will not hurt use cases where stable
UUID does not matter, and will definitively help when stable UUID is
important. For these evaluated objects UUID will be not resetable - once
it generated, it will stay the same even if generated again. But I
cannot think of a scenario where this would be an issue (especially if
it would be possible to reset UUID of original datablock - could be
useful if working with a copy of .blend file to make sure all UUIDs are
globally unique).
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